1. Field of the Invention
The present invention relates to a method of forming an organic film, and to a nozzle plate, an inkjet head and an electronic device, and more particularly to technology for forming an organic film using a silane coupling agent.
2. Description of the Related Art
An organic film using a silane coupling agent can be formed on various base members, and therefore is applied in a wide range of fields. In the field of inkjet technology, a film of this kind is used when forming a liquid-repellent film on the ejection surface of a nozzle plate, or when bonding two base members together, or the like, and beneficial effects are achieved in improving the ejection characteristics, the maintenance properties and the durability of the head.
A monomolecular film or polymerized film using a silane coupling agent is bonded to the base member through siloxane bonds (Si—O bonds). The siloxane bonds are liable to be hydrolyzed in alkaline solutions, and upon contact with alkaline solutions, are liable to be erased from the base member. Hence, there is a problem in that durability is poor in respect of alkaline solutions.
In response to these problems, Japanese Patent Application Publication No. 2003-286478, for example, describes a liquid-repellent film made of a material which incorporates a substitute group that makes it harder for alkaline components to approach the vicinity of the siloxane bonds, and a substitute group having thermal resistance, with the object of providing the liquid-repellent film having high resistance to alkalis and high thermal resistance. Moreover, Japanese Patent Application Publication No. 2009-029068 is directed to a method of manufacturing a nozzle plate for liquid ejection having a liquid-repellent film arranged on a surface where ejection ports for ejecting the liquid are present, and describes a method of manufacturing a nozzle plate by activating the surface of a silicon substrate having a silicon oxide film by removing the surface by chemical reaction, and then activating by physical breakdown, and arranging a liquid-repellent film on the silicon oxide film.
However, even if the material properties of the liquid-repellent film are improved and durability in terms of resistance to alkalis is improved, as in Japanese Patent Application Publication No. 2003-286478, there is a drawback in that if the processing of the underlying layer is incomplete, then sufficient bonding sites (hydroxyl groups: OH groups) are not created. Then, the bonding between the liquid-repellent film and the underlying layer is not sufficient, and the film properties are declined. Moreover, even if the silicon oxide film of the underlying layer is subjected to the plasma treatment to remove organic material and the surface is cleaned and activated to strengthen the bond between the liquid-repellent film and the underlying layer as in Japanese Patent Application Publication No. 2009-029068, there is a drawback in that sufficient reaction sites are not created on the surface and a high-density liquid-repellent film having sufficient resistance to alkalis is not obtained.